Patent Application
20240044454
This invention generally relates to a collapsible container used to provide fluid flow in low, micro, or non-gravitational environments. The container accomplishes the flow of fluid in any gravitational environment using specific structural components of the container.
Storage of space flight fuels presents a specific problem in microgravity environments. The problem of evacuating a fuel storage tank currently relies on a propellant management device (“PMD”). The PMD enables a process by which fuel is expelled from a reservoir in a low-gravity or microgravity environment. PMDs can rely on a number of mechanisms to function however surface tension is used as a primary expulsion device, in combination with baffles, fins, and vanes. The resultant goal of a PMD is to provide liquid fuel to rocket engines without adding gas to the liquid fuel. PMD cannot utilize the forces of gravity or buoyancy to determine or utilize fuel levels within a storage container. Furthermore, the position of fuel is normally determined by surface tension, where the liquids coalesce to form a gaseous bubble located in the center of the container. PMD must deliver gas free liquid fuel to the engine in order to operate.
A PMD can be grouped in two types, a total communication PMD or a control type PMD. A total communication PMD acquires propellant from anywhere it is located within the container. Total communication PMDs can utilize vanes, gallerys, or pleated liners to enhance transport of liquid. Vanes are used for situations where there are low propellant needs, for instance in low acceleration periods. The mechanical features allow for either fuel delivery to engines or other PMD features. The vanes enable transport of the liquid fuel to tank outlets. The length and shape of the vanes is dependent on the container and can be dependent on the specific use. Center posts may be added in addition to the vanes to direct fluid flow.
Furthermore, control-type PMDs can be used to provide engines with propellant. The control-type PMDs include sponges, troughs, and traps. Sponges are used to normally provide propellant to ignition sources. Propellant transfer in microgravity is a problem that requires specific solutions. PMDs ensure that vapor-free propellant is supplied from a source tank (e.g. a fuel depot) to a receiver tank or engine. Failure to do so for engines will result in combustion inefficiencies and even engine failure. At the present however, most traditional surface tension based PMDs face difficulties when handling cryogenic liquids due to several limitations.
Cryogenic bladders were initially investigated by NASA and several government contractors in the 1960s and 70s. The bladders would encapsulate propellant within spherical bags of polyethylene terephthalate (PET, Mylar®) and polyimide (Kapton®) film, fabricated by epoxying strips of polymer film together. To expel propellant, the bladder would stochastically buckle and crumple. Research into these bladders discontinued after benchtop testing of the PMD found mixing of the liquid hydrogen (LH2) and helium. There were several conjectures as to why this occurred: bulk permeation through the bladder material, tears in the bladder, or improper sealing. Thus, tearing or sealing issues were likely the reason as to the technology not being pursued further and the reduced interest and viability of a cryogenic bladder as a solution to this issue.
Novel solutions that can provide storage and evacuation of cryogenic fluids in various gravitational environments are needed.
The present disclosure provides a storage system for cryogenic fluids. In one aspect, the system comprises a housing delimiting a cavity therein and a collapsible container disposed within the cavity and coupled to a surface of the housing, wherein the collapsible container is configured to contain a fluid. An inlet allows for a pressurant to be added to the space between the wall of the housing and the collapsible container. In doing so, the pressure of the space between the housing and the container increases causing the container to assume a collapsed state. An outlet fluidly coupled to the collapsible container is configured to dispense the fluid out of the collapsible container and housing.
In some embodiments, the collapsible container comprises a plurality of panels which are foldable at flexure hinges. In some embodiments, the panels have an average thickness of at least 0.1 μm. In some embodiments, a thickness of the flexure hinges is less than a thickness of the panels. In some embodiments, a radius of curvature of a first portion of the flexure hinges is smaller than a thickness of the panels. In some embodiments, a radius of curvature of a second portion of the flexure hinges is larger than a thickness of the panels.
The plurality of panels may be arranged in at least one of a hexagonal structure and an isogrid structure. In some embodiments, the collapsible container is configured to form a folded pattern when collapsed, wherein the folded pattern includes at least one of a Yoshimaru pattern, a Kresling pattern, a Miura-ori pattern, an accordion pattern, and a hexagonal pattern. In some embodiments, the collapsible container comprises a plurality of channels within the panels of the container configured for flowing a coolant. In some embodiments, the collapsible container is formed from an impermeable material. In some embodiments, the impermeable material is a polyimide, polyethylene terephthalate, or fluropolymer film.
Another aspect of the disclosure provides a storage system in which the collapsible container is not surrounded by a rigid housing. The system may comprise at least one collapsible structure comprising a plurality of panels which are foldable at flexure hinges, wherein the structure is configured to hold a cryogenic fluid therein and is configured to collapse when an external or internal force is applied to the structure, and an outlet fluidly coupled to the collapsible structure, wherein the outlet is configured to dispense the cryogenic fluid out of the collapsible structure. In some embodiments, the system further comprises one or more of a mechanical actuator, a piston, or a pump configured to apply the force to the structure. In some embodiments, the at least one collapsible structure includes a plurality of layered collapsible structures. In some embodiments, the container is configured to distribute a pressurant between an outer layer and an inner layer.
Another aspect of the disclosure provides a method of delivering fluid, comprising loading a cryogenic fluid into a collapsible container in a deployed state, applying a fluid pressure to an exterior of the collapsible container in the deployed state, wherein the fluid pressure provides movement from the deployed state into a collapsed state of the collapsible container, and flowing the cryogenic fluid out of the collapsible container as the container moves from the deployed state to the collapsed state.
Another aspect of the disclosure provides a method of manufacturing a collapsible container as described herein, comprising providing a mold having a predetermined geometry, arranging a polymeric film above the mold, heating the polymeric film, pressing the mold into the polymeric film while applying a vacuum to the polymeric film such that the polymeric film assumes a shape of the mold, and removing the polymeric film from the mold.
The foregoing and other objects, features, and advantages of the present disclosure will become more apparent from the following detailed description, which proceeds with reference to the accompanying figures.
The following drawings form part of the present specification and are included to further demonstrate certain aspects of the present invention. The invention may be better understood by reference to one or more of these drawings in combination with the detailed description of specific embodiments presented herein.
The following are definitions of terms that may be used in the present specification. The initial definition provided for a group or term herein applies to that group or term throughout the present specification individually or as part of another group, unless otherwise indicated.
Additionally, it will be understood that any list of such candidates or alternatives is merely illustrative, not limiting, unless implicitly or explicitly understood or stated otherwise.
As used in this specification and the appended claims, the singular forms “a”, “an” and “the” include plural referents unless the content clearly dictates otherwise. The use of the word “a” or “an” when used in conjunction with the term “comprising” in the claims and/or the specification may mean “one,” but it is also consistent with the meaning of “one or more,” “at least one,” and “one or more than one.”
Throughout this application, the term “about” is used to indicate that a value includes the standard deviation of error for the device or method being employed to determine the value.
The use of the term “or” in the claims is used to mean “and/or” unless explicitly indicated to refer to alternatives only or the alternatives are mutually exclusive, although the disclosure supports a definition that refers to only alternatives and “and/or.”
As used in this specification and claim(s), the words “comprising” (and any form of comprising, such as “comprise” and “comprises”), “having” (and any form of having, such as “have” and “has”), “including” (and any form of including, such as “includes” and “include”) or “containing” (and any form of containing, such as “contains” and “contain”) are inclusive or open-ended and do not exclude additional, unrecited elements or method steps.
In addition, unless otherwise indicated, numbers expressing quantities of ingredients, constituents, reaction conditions and so forth used in the specification and claims are to be understood as being modified by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the subject matter presented herein. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the subject matter presented herein are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical values, however, inherently contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.
Described herein are collapsible container based systems that are an attractive alternative to surface-tension PMDs for handling cryogenic liquids. The collapsible containers comparatively may 1) allow higher expulsion flow rates than vanes and sponges, 2) significantly reduce operational complexity, and 3) thermally insulate the propellant from environmental heat leaks.
Furthermore, while historical cryogenic containers suffered from the low ductility of polymer films at cryogenic temperatures, the present disclosure shows that the incorporation of folded patterns (a compliant mechanism) into the collapsible container increases the reusability of the cryogenic PMD.
The cryogenic propellant systems possess unique challenges that make expulsion collapsible containers more desirable for certain applications. Cryogens have lower surface tensions than room-storable propellants: at 20.4 K, hydrogen possesses a surface tension 34 times smaller than that of hydrazine at 303 K. This low tension further decreases the already limited flow rates vanes and sponges can sustain for liquid exiting a tank. It is difficult for PMDs to handle flow rates required for cryogenic fuel systems. As expulsion collapsible containers do not rely upon surface tension (a collapsible container instead mechanically pumps the liquid when subjected to a pressure gradient), the disclosed systems and methods have the advantage of functioning at high flow rates.
Gallery arms have been used previously to meet high flow rate demands of future cryogenic propulsion systems. These PMDs primarily use porous screens to maintain phase separation within the tank, the behavior of which is governed by the bubble-point pressure. This parameter determines the maximum sustainable expulsion flow rate. However, gallery arms are complex systems, resulting in lower reliability. Complications arise when expelling propellant from the tank because of thermal and mass transfer, e.g. evaporation/condensation, at the pressurant-propellant interface as seen in
A collapsible container as described herein simplifies the expulsion process. By arranging a non-porous membrane between the propellant and gas, mass transfer between the two phases is inhibited by the impermeability of the membrane.
With reference to
The collapsible container 10 may be formed from a plurality of panels 12 which are foldable at flexure hinges 14. A flexure hinge is a flexible region between two adjacent rigid panels that undergo relative limited rotation in a mechanism (
With reference to
With reference to
In some embodiments, the collapsible container is formed from a material selected from a polyimide (e.g. Kapton®), polyethylene terephthalate (PET, Mylar®), polyetheretherketone (PEEK), polytetrafluoroethylene (Teflon®), fluorinated ethylene propylene (FEP), and perfluoroalkoxy (PFA). Extrapolation with the Arrhenius equation (from an empirical data set between 300-150 K) suggests that the permeability of Kapton® films to helium gas at 20 K is 36 orders or magnitude lower than it is at 300 K. Thus, using Kapton® and other polymers for the collapsible container material allows for an effective elimination of the mass transfer at cryogenic temperatures.
Impermeable materials also prevent pressurant from dissolving into the propellant in significant quantities during long-duration missions. The pressurant solute could adversely affect engine performance (e.g. induce cavitation at the turbo-pumps for a pump-fed system). Assuming no mixing within the tank, this is not an issue for mission lengths of several hours, where the equilibrium solubility of pressurant molecules/atoms in the liquid is not approached in that time period. As an example, the slow diffusion of helium into liquid methane requires 6 hours for the helium concentration wave to appreciably traverse 1 cm from the liquid-vapor interface. Behavior for helium diffusion in liquid hydrogen (LH2), or nitrogen diffusion in liquid oxygen (LOX), are potentially similar. However, over greater time periods, these equilibrium solubilities become relevant. And if higher pressure tanks are implemented during long duration missions, equilibrium solubilities could be higher, exacerbating any resulting issues.
As used herein, “impermeable” refers to the production of a gas transmission rate of of ≤1*10−8 mol/s/m2.
The collapsible container is sized to hold a volume of liquid, e.g. cryogenic fuel, of about 10−8-107 liters.
With reference to
The Yoshimaru pattern is a triangular mesh buckling pattern which produces a corrugated shape resembling the Schwarz lantern. The Kresling pattern is a cylindrical origami pattern comprising identical triangular panels with cyclic symmetry, functioning under the spontaneous buckling of a thin cylindrical shell under torsional loading. The crease patterns of the Miura-ori pattern form a tessellation of the surface by parallelograms. In one direction, the creases lie along straight lines, with each parallelogram forming the mirror reflection of its neighbor across each crease. In the other direction, the creases zigzag, and each parallelogram is the translation of its neighbor across the crease. Each of the zigzag paths of creases consists solely of mountain folds or of valley folds, with mountains alternating with valleys from one zigzag path to the next. Each of the straight paths of creases alternates between mountain and valley folds. The flat pattern may be curved along the x-axis to provide for a collapsible container as described herein. The accordion fold utilizes a series of valley, mountain, and inside reverse folds.
In the operation of the storage system described herein, a cryogenic liquid is loaded into the collapsible container in a deployed state, e.g. via the outlet 40. A fluid pressure is then applied to an exterior of the collapsible container, wherein the fluid pressure (i.e. pressurant) provides movement from the deployed state into a collapsed state of the collapsible container. The movement of the container into the collapsed state causes the cryogenic fluid to flow out of the collapsible container via outlet 40.
As used herein, a “pressurant” is a fluid (liquid or gas) that when dispered into the cavity provides an external pressure on the collapsible structure causing the container to assume a collapsed state. Exemplary pressurants include, but are not limited to, helium, nitrogen, hydrogen, oxygen, and methane. In some embodiments, the pressurant provides a pressure of at least 1-300 kPa.
The interior of the collapsible structure is configured to contain fuel which may comprise a propellant, such as a gas or liquid propellant which may be compressed. A propellant is a mass that is expelled or expanded in such a way as to create a thrust or other motive force. In some embodiments, the byproducts of substances used as fuel may be used as a reaction mass (propellant).
In electrically powered spacecraft, electricity is used to accelerate the propellant. An electrostatic force may be used to expel positive ions, or the Lorentz force may be used to expel negative ions and electrons as the propellant. Electothermal engines use the electromagnetic force to heat low molecular weight gases (e.g. hydrogen, helium, ammonia) into a plasma and expel the plasma as propellant. In the case of a resistojet rocket engine, the compressed propellant is simply heated using resistive heating as it is expelled to create more thrust.
In chemical rockets and aircraft, fuels are used to produce an energetic gas that can be directed through a nozzle, thereby producing thrust. In rockets, the burning of rocket fuel produces an exhaust, and the exhausted material is usually expelled as a propellant under pressure through a nozzle. The exhaust material may be a gas, liquid, plasma, or a solid. In powered aircraft without propellers such as jets, the propellant is usually the product of the burning of fuel with atmospheric oxygen so that the resulting propellant product has more mass than the fuel carried on the vehicle.
In chemical rockets, chemical reactions are used to produce energy which creates movement of a fluid which is used to expel the products of that chemical reaction (and sometimes other substances) as propellants. For example, in a simple hydrogen/oxygen engine, hydrogen is burned (oxidized) to create H2O and the energy from the chemical reaction is used to expel the water (steam) to provide thrust. Often in chemical rocket engines, a higher molecular mass substance is included in the fuel to provide more reaction mass.
Rocket propellant may be expelled through an expansion nozzle as a cold gas, that is, without energetic mixing and combustion, to provide small changes in velocity to spacecraft by the use of cold gas thrusters, usually as maneuvering thrusters.
Exemplary propellants include, but are not limited to, cryogenic oxygen, hydrogen, hydrocarbon, ethanol, methane, hydrogen peroxide, kerosene, red fuming nitric acid, unsymmetrical dimethylhydrazine, dinitrogen tetroxide, hydrazine, and mixtures thereof.
In long-term missions, it is desirable to limit heat flux into the cryogenic propellant. Traditionally, liquid is in direct contact with the walls, so stray heat leak into the tank directly evaporates and/or boils the liquid cryogen. Active thermal control systems can remove this heat leak at the cost of increased system mass. This trade-off is exacerbated by surface tension PMDs in contact with the tank wall, such as vanes. These PMDs may act like fins and conduct heat into the bulk liquid. Collapsible containers instead insulate the propellant and reduce heat flux.
With reference to
The combination of high expulsion flow rates, a barrier against mass transfer, and inherent thermal insulation make the cryogenic collapsible container a simple and high performing alternative to existing cryogenic PMDs. This is particularly true for long-duration missions seen by fuel depots and in-space rocket engines traveling to the Moon or Mars, which require the use of mass and cost expensive thermal control systems to prevent/reduce propellant boil off.
Further embodiments of the disclosure include methods for making a storage system as described herein. To manufacture a collapsible container, several key metrics must be met. First, the structure must be liquid tight to prevent fuel from leaking. Second, the process must repeatably produce high quality storage systems with consistency between the collapsible containers/bladders. Finally, the manufacturing process should allow for a wide range of volumes to meet demands of various applications. A vacuum forming manufacturing method fulfills these three criteria.
In some embodiments, to vacuum form a collapsible container, a mold is 3D printed or machined into the desired geometry (
During the vacuum forming process, many different polymeric materials can be used, including fluoropolymers, such as Fluorinated ethylene propylene (FEP) and Perfluoroalkoxy (PFA) and other polymers such as polyimide (e.g. Kapton®), polyethylene terephthalate (PET, Mylar®), polyetheretherketone (PEEK), and polytetrafluoroethylene (Teflon®). Bladders that are vacuum-formed from these materials can be used for storage of fluids such as liquid hydrogen, liquid oxygen, and other propellants/fluids as described herein. These materials have been demonstrated to survive 1000s of cycles within the cryogenic regime, at least when fabricated via hand-folding.
It should be emphasized that the above-described embodiments and following specific examples of the present invention, particularly, any “preferred” embodiments, are merely possible examples of implementations, merely set forth for a clear understanding of the principles of the invention. Many variations and modifications may be made to the above described embodiment(s) of the invention without departing substantially from the spirit and principles of the invention. All such modifications and variations are intended to be included herein within the scope of this disclosure and the present invention and protected by the following claims.
Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limit of that range and any other stated or intervening value in that stated range, is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included in the smaller ranges and are also encompassed within the invention, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the invention.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present invention, representative illustrative methods and materials are now described.
All publications and patents cited in this specification are herein incorporated by reference as if each individual publication or patent were specifically and individually indicated to be incorporated by reference and are incorporated herein by reference to disclose and describe the methods and/or materials in connection with which the publications are cited. The citation of any publication is for its disclosure prior to the filing date and should not be construed as an admission that the present invention is not entitled to antedate such publication by virtue of prior invention. Further, the dates of publication provided may be different from the actual publication dates which may need to be independently confirmed.
As will be apparent to those of skill in the art upon reading this disclosure, each of the individual embodiments described and illustrated herein has discrete components and features which may be readily separated from or combined with the features of any of the other several embodiments without departing from the scope or spirit of the present invention. Any recited method can be carried out in the order of events recited or in any other order which is logically possible.
The invention is further described by the following non-limiting examples which further illustrate the invention, and are not intended, nor should they be interpreted to, limit the scope of the invention.
The hydrogen permeability of polymer films between 20-200 K can be determined using a permeation test cell as shown in
A fatigue test of the collapsible container may be performed using a Gelbo-flex tester as shown in
While the invention has been described in terms of its preferred embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the appended claims. Accordingly, the present invention should not be limited to the embodiments as described above, but should further include all modifications and equivalents thereof within the spirit and scope of the description provided herein.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2022/015563 | 2/8/2022 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 63146794 | Feb 2021 | US |
